Additive manufacturing or 3D printing is a process of making three dimensional solid objects with a high degree of freedom of the design according to a 3D virtual module. Basically the object is created by providing layers of material to a substrate or a platform whereby the final object can have a layered material structure. The object can be made by additive manufacturing in total without being one piece of material with the substrate.
Today several additive technologies are known, for example selective laser sintering, direct metal laser sintering, fused deposition modeling, stereo lithography, digital light processing, fused filament fabrication, melted and extrusion modeling, laminated object manufacturing, electron beam melting, selective heat sintering or powder bed and ink head 3D printing.
From DE 44 00 315 CI it is known to lithographically add layers of material to a part to build a micro-structure. A high degree of accuracy is needed to avoid any significant offset in channels extending from a substrate into the added material.
From US 2007/0275210 A1 it is known to layerwise generate a honeycomb seal.
From EP 1295846 a multilayered microdevice structure comprising channels is known.
This invention concentrates on additive technologies which enables the generated composite part to be used in a gas turbine burner. The most interesting technologies are therefore selective laser sintering, direct metal laser sintering or fused deposition modeling. Since these additive technologies are comparatively young developments, design adjustments have not been performed so far to optimally exploit the advantages of these technologies as is done for conventionally produced parts. Conventional production here means mature technology for example casting, milling or turning.
Especially advantageous is additive manufacturing in the field of service and refurbishment for example of burner heads of gas turbines. If a burner head of a gas turbine made to inject fuel and maybe oxygen containing gas into a combustion chamber is worn out by for example erosion, it is conventionally completely replaced. By using additive manufacturing a part of this burner head can be cut off and the remaining part can be used as a substrate for additive manufacturing, for example selective laser melting.
Here it is, however, very difficult to adjust the position of the used part accurately to guarantee that tiny channels in the first existing part are placed correctly to be continued by the second part to be generated by the additive manufacturing onto the substrate. Normally the aim is to exactly continue these channels extending through the old piece of material into the new piece of material across the interface between these two parts without any position shift restricting the average diameter of said channel at the interface. It is therefore up to now not an interesting option to rework such parts as described above since an offset can merely be avoided.